Syzdekistan

My estimate about the relative brightness of last week’s lunar eclipse was wrong (hey, it was behind a cloud!). It turns out that the brightness of the moon during eclipses is dependent on the path the moon takes through the earth’s shadow and the clarity of the earth’s atmosphere. In fact, there is a scale to measure the brightness of the moon during eclipses and here is a chart of eclipse brightness over time and a comparison of a normal eclipsed moon and a very dark, almost invisible moon, which was taken during the December 30, 1963 eclipse. This eclipse occurred after a volcanic eruption.

Pinatubo was by no means the first volcano to tarnish the coppery glow of a lunar eclipse. Many who saw the Dec 1992 eclipse compared it to the dark eclipses of Dec 1982 and Dec 1963. The culprit volcanoes for those eclipses were El Chichon (Mexico) in 1982 and Gunung Agung (Bali) in 1963. An eclipse so dark as to be invisible followed the triple eruptions in 1902 of Pelee and Soufriere in the Caribbean and Santa Maria in Guatemala. A very dark eclipse in Oct 1884 followed the celebrated eruption of Krakatoa a year earlier. Other dark eclipses following major volcanic eruptions were recorded during the 19th, 18th, and 17th centuries. In 1620, Johannes Kepler observed an eclipsed Moon so dark that “nothing could be seen of it, though the stars shone brightly all around”, and although he was unaware of any volcanic eruptions, he correctly attributed the darkness to “mists and smoke” in the Earth’s atmosphere. It may have been another unknown volcanic upheaval around A.D. 753 that ultimately led a reporter for the Anglo-Saxon Chronicle to describe the eclipsed Moon that year as “covered by a horrid black shield”, in contrast to a more normal eclipse appearing “sprinkled with blood” 13 years earlier. (Link)

Richard Keen at the University of Colorado (link) is using the brightness of the moon during eclipses to determine the effects of volcanos on the world’s climate.